Symphony in C might never evolve into an authoritative baroque-music orchestra, but you couldn't begrudge its right to the Pergolesi

Stabat Mater

on Saturday at Camden's Gordon Theater: Where else can one hear this showcase for two vocal soloists and orchestra? And though countertenors do seem to grow on trees these days, the young Anthony Roth Costanzo made an important local debut.

In its rehabilitated state, the Stabat Mater allows such discoveries: Though known previously in a corrupt edition for amateur choruses, the Stabat Mater was written for two accomplished vocal soloists in 12 concise solo arias and duets that meditate on the grief of the Virgin Mary - in a distillation of baroque opera that goes to the heart of matters without recitatives or gratuitous vocal display.

Costanzo's larger-than-usual baroque voice suggests a future in the mezzo-soprano sections of Mahler's Das Lied von der Erde. In fact, he's cast in the Opera Company of Philadelphia's production of Henze's Phaedre this season - in keeping with his intriguingly varied career, which includes a touring production of Broadway's Falsettos and the Merchant-Ivory movie A Soldier's Daughter Never Cries.

Costanzo's vocal richness both blends with and envelops other voices, the way a good concert organ gives a subtle added heft to a larger orchestral texture. His fortissimos boom a bit - a luxury problem considering the fragile sound of past-generation countertenors.

Soprano soloist Sarah Moulton, also a newcomer with a past in musical theater, has a fine sense of baroque style, though the voice is still emerging and promises richer vocal colors in the future. Both need to pay closer attention to words.

Under music director Rossen Milanov, Symphony in C played Pergolesi and the Vivaldi Concerto for Four Violins and Cellos capably but in a generalized way, treating rhythms without much sense of where they can take a piece and lacking phrase specificity.

The musicians' hearts were in Brandenburg Gate, a 2008 piece by Paul Moravec that sounds nothing like Bach but seizes upon Bachlike mechanics with a lot of fine-tooled, hardworking musical elements that don't seem to be in cahoots with one another but are. The piece was also inspired by the 1989 reopening of Berlin's Brandenburg Gate, and the exhilaration that accompanied that event is heard in unexpected triumphs of logic, both macro and micro.

The orchestra definitely grooved on the piece, which easily takes its place alongside neo-baroque works by Stravinsky and Ellen Taaffe Zwilich that look back to the past without leaning on it.

Contact David Patrick Stearns

at dstearns@phillynews.com.